Production of steroid intermediate



United States Patent 0 "ice Patented 52221? 1 2 2,802,873 ful in theproduction of steroids, particularly the adrenal PRODUCTION OF STEROIDINTERMEDIATE cortical hormones such as cortisone.

In the following outline of the methods of the invention Robert WoodwardBelmont Mass" assign 9 reference is had to the illustrative sequence ofnovel comsearch Corporation, New York, N. Y., a corporation of 5 poundsof the invention.

New York V In the structural fontnulas in the chart, methyl groups NoDrawmg' .Apphcatlon 1951 attached to carbon atoms common to two ringsare insenal 220977 dicated by the conventional line extending from thecar- 1 Claimbon atom, and Ac indicates the residue of an organic Thisinvention relates to methods and compounds use- 10 carboxylic acid, suchas acetic acid.

(v1 (V) (iv (VII (VIII) (IX) C H: Q l) Z ZZZ (g 1 H--N O H:

(XIVb) (XVa) (XVb) l CH l 1 Q o i Q 0 /CH3 0 C 0 \OH: I I o (XVII) (XVI)CHO CH:-CHO (\l/ 1 I 0 0111 -0110 f o (XVIII) (XIXa) i CHO (XIXb) Thecis-adduct (M. P. 93-95 C.) obtained by the Diels- Alder condensation of1,3-butadiene and Z-methyl-S- methoXy-benzoquinone is converted to thetrans-adduct, trans 2 methoxy 9 methyl 5,8,9,10 tetrahydro1,4-naphthoquinone (I) by dissolving in an aqueous alkaline solution indioxane and acidifying after seeding with the transisomer.

The trans-adduct is reduced to the corresponding glycol (II) withlithium aluminum hydride, and the glycol is converted to the ketol,l-l1ydroXy-2-keto-9-methyl-1,2,5,8,9, IO-hexahydronaphthalene (III), bytreatment with a dilute mineral acid. The ketol is then esterified (IV)with any organic carboxylic acid, for example, acetic acid.

The ketol ester (IV) is reduced by treatment with zinc in aceticanhydride or in an inert organic solvent to 2- keto-9 methyl1,2,5,8,9,10 hexahydronaphthalene (V). The bicyclic ketone (V) isformylated at position 1 to give the l-hydroxymethylene derivative (VI),which is condensed with ethylvinylketone to give l-aldehyde-l- (Bbutyroethyl) 2 keto 9 methyl 1,2,5,8,9,1O hexahydronaphthalene (VII).

Treatment of compound (VII) with mild condensing agents such aspotassium hydroxide in an aqueous organic solvent or hydrogen chloridein acetic acid converts it to the tricyclic ketone,1,14-dimethyl-2-keto-2,3,4,5,8,12,13, 14-octahydrophenanthrene (VIII),which has the desired anti-trans configuration.

The tricyclic ketone (VIII) is oxidized to the 6,7-glycol (IX).Oxidation with osmium tetroxide typically gives the two cis-isomers bothof which are usable in the succeeding steps of the method. Otheroxidizing agents may give the trans-isomers, which may also be used inthe succeeding steps. Perbenzoic acid gives the 6,7-oxide whichhydrolyzes to the trans-glycols. Silver benzoate .asoasvs and iodinegives the dibenzoate of the glycol. Hydrogen peroxide may also be usedas the oxidizing agent, for ex ample, with osmium tetroxide as catalyst.

The hydroxyl groups of the glycol (IX) are protected by reaction with aketone, such as acetone, (X) and protected compound hydrogenated at the9,10-double bond, for example, with hydrogen at atmospheric pressure ina non-polar solvent, such as dry benzene, in the presence of ahydrogenating catalyst, to produce the dihydro derivative (XI), which isformylated at position 3 (XII). The formyl group of compound (XII) isprotected by reacting it with a secondary amine, such as methylaniline,to give the methylanilino derivative (XIII).

Compound XII is reacted with acrylonitrile in the presence of aquaternary nitrogen base to give the isomeric 'cyanoethyl compounds XIVaand XIVb, which are preferably not separated at this stage but arehydrolyzed to the corresponding carboxyethyl compounds. The keto acidsmay be separated by taking them up in either. A keto acid (XVa) meltingat 150 C. (labile) and 170 C. (stable) crystallizes from the ether andthe other isomeric keto acid (XVb) is obtained as an oil by evaporationof the ether. The oily acid has the desired configuration at asymmetriccarbon atom l.

The keto acid (XVb) is convertedto the enol lactone (XVI), for example,by boiling with acetic anhydride in the presence of a small amount ofsodium acetate. The

lactone (XVI) is now converted to the tetracyclic ketone (XVII), havinga D-homosteroid ring structure by con densing with a methyl magnesiumhalide, decomposing the addition product with acid and treating theproduct thus obtained with dilute aqueous alkali in a watermiscibleorganic solvent. 7

The homo-D-ring of ketone (XVII) may now be converted to a cyclopentanoring by opening and reclosing the ring, for example, by the followingsteps: The ketone (XVII) is oxidized, for example, with H104, to thedialdehyde (XVIII), 1,2-bis (aldehydomethyl)-2,l3-dimethyl 7 keto1,2,3,5,6,7,9,10,11,l3 deeahydrophenanthrene, and the dialdehyde iscondensed to the 17-aldehyde steroid, A9,( 1 1,16-bisdehydro-2l-norprogesterone (XIX). Some of the isomeric15-aldehyde (XIXai) is also formed. The aldehydes XIX and XlXa have thesame steric configuration at the asymmetric carbon atoms as the naturalsteroid hormones of the adrenal cortex such as cortisone and may beconverted into these hormones by already available procedures.

The following specific examples are illustrative of the methods andcompounds of the invention:

Isomerizatio-n of the .cis-adduct to the .tmns-aa'duct Sixty grams ofthe cis-adduct (M. P. 9395 C.) obtained by the Diels-Alder condensationof 1,3-butadiene and Z-methyl-S-methoxybenzoquinone, purified .byrecrystallization and almost colorless, is dissolved in 80 ml.

of dioxane. Solution is facilitated by warming to 10-50 C. Five per centmore than the calculated amount of about 1 N sodium hydroxide solution(312 ml., 0.975 N) is added over 10 min. with stirring in an atmosphereof nitrogen. A brownish orange solution containing about 1 ,g. ofsuspended solid is obtained. This solution .is diluted by the additionof .600 ml. of water and then seeded with 3 g. of finely powderedtrans-adduct (M. 'P. 125-l27 C.). At this point it is essential toascertain that most of the seed has remained undissolved. If there beexcess alkali present, the seed material will of course .go intosolution; in that case more trans-adduct should be added till there isan appreciable amount of undissolved solid in suspension. About 1 Nhydrochloric acid is added dropwise to the seeded solution with vigorousstirring; a solid starts to separate immediately. Addition of acid 'isstopped when the solution changes color to lemon yellow indicatingcomplete neutralization (pH 5) of the base. Some more water (200 ml.) isadded and the solid product is collected by filtration, washed fourtimes with water and dried. A finely granular, light tan colored solid,M. P. 126-129 C., is obtained. This material is pure enough for use inthe next step without further purification.

Glycol (II).The trans-adduct (I) (130 g.) in dry pure redistilledtetrahydrofuran ('1 l.) is slowly added to a stirred solution of lithiumaluminum hydride ('24 g.) in dry ether (1.4 l.) in an atmosphere ofnitrogen. The addition is controlled so as to keep the mixture refluxinggently (addition time ca. 2 /2 hrs). During the addition a viscoussticky complex separates onto the stirrer, making stirring diflicult.The complex towards the end of the addition becomes more granular, andat the end a suspension of .a white powder is. obtained. Stirring is Thewhite suspension soon becomes light yellow. During the entire additionof saturated sodium sulphate solution,

rapid stirring is continued so that the LIA1H4 complex clinging to thesides of the flask may be washed down. Addition of the saturatedsolution is. continued until the precipitate. becomes slightly wet (atwhich time it starts clinging to the sides of the flask). Withoutstopping the stirring about 200 gms. MgSO4(anhyd.) are added. Rapidstirring is continued for another 1.0 minutes. The precipitate is thenfiltered from the etheral solution and washed thoroughly with excessethyl ether. The filtrate and washings are concentrated, last traces ofsolvent removed at the water pump, and the viscous oil obtained isdiluted with a small amount of ethyl ether and allowed to crysta llizein the refrigerator overnight. The crude glycol melts at about 128-133C.

Ketol (lIl).The crude glycol (68 .g.) is dissolved in reagent gradedioxan (375 cc.), and 2 N sulfuric acid (300 cc.) is added. The solutionis allowed to stand for 24 hours at room temperature and is thenpouredinto ether and water. The aqueous layer is washed twice more withether, the combined ether solutions are washed with sodium bicarbonatesolution, and the latter extract is again extracted with ether. Thecombined etheral layers are washed once with salt solution, dried(MgSO4), and evaporated. The remaining dioxan is completely removed onthe water pump. The residue consisting of the crude ketol, partlysolidifies on being seeded with a specimen of pure ketol (M. P. 71-72C.).

Ketol acetate (IV) .The crude ketol (58 g.) is dissolved in dry pyridine(300 cc. reagent grade pyridine kept over potassium hydroxide forseveral days), and acetic anhydride (60 cc. reagent grade) is added. Thesolution-from which moisture is excluded by a calcium chloride tube, isheated on the steam bath for afew min utes, and is then set asideovernight. Most of the pyridine is removed from the red solution at thewater pump, other is added to the residue and the solution is washedwith water, excess dilute sulfuric acid, sodium bicarbonate and finallywater. Each aqueous washing is extracted with ether, and the combinedether solutions are dried and evaporated. The crude acetate remains as arather mobile orange oil.

Bicyc'lic ketone (V).The crude acetate (60 g.) and redist'illed aceticanhydride (550 cc.) are heated to .145- C. in a parafiin bath withstirring under reflux, with the exclusion of moisture. Commercial zincdust (550 g.) is added all at once, and the mixture is stirredvigorously at this temperature for 8 minutes. The mixture is cooled inice with stirring, the zinc is removed by filtrati-on and thoroughlywashed with ether. The ether is evaporated on the stem bath, and theacetic anhydride is distilled off on the water pump. The light yellowresidue (ca. 110 g.) containing some solid is diluted with ether,

and washed with water, dilute sulfuric acid and again water. The aqueouslayers are extracted with ether, and the combined ether solutions arewashed twice with sodium carbonate solution (each time for ca. mins.)and then with water. The combined aqueous layers are washed with ether,the combined ether extracts are dried (MgSO4) and evaporated. Theresidue is distilled roughly into two fractions:

(a) B. P. 6898 C./0.4 mm. and (b) B. P. 1l7-137 C./0.4 mm.

Fraction (a) is redistilled slowly through a small Vigreaux column togive the bicy-clic ketone (V) as a colorless mobile liquid, B. P. 80-81C./0.8 mm., 12 1,5167. On being seeded at room temperature (25 C.) itnearly completely solidifies, M. P. 26-29" C.

' Hydroxymethylene ketone (Vl).-Commercial sodium methoxide (35 g.) iscovered with dry benzene (175 cc.) and redist-illed ethyl formate (87cc.) is added in a thin stream to the stirred mixture at roomtemperature in a nitrogen atmosphere. Stirring is continued at roomtemperature for a further /2 hour, when the mixture is cooled in ice.The bicyclic ketone (35 g.) in dry benzene (175 cc.) is added dropwiseduring 45 minutes with ice-cooling. More benzene (175 cc.) is added, andstirring in nitrogen is continued for a further 12 hours at roomtemperature. About 30 minutes after the end of the addition a'voluminousyellow gelatinous precipitate separates, which does not change inappearance when the reaction was terminated. Ether and iced dilutesulphuric acid are added, the aqueous layer is washed with ether, andthe combined etheral layers are washed with excess potassium hydroxidesolution. The red-brown alkaline aqueous layer is washed once withether, acidified with dilute hydrochloric acid, and extracted twice withether. The latter ether washings are washed once with water, dried, andevaporated. The residue contains some formic acid, and is thereforedistilled through a small Vigreux column. This yields thehydroxymethylene ketone (VI) as a yellow mobile liquid, B. P. 8890C./0.015 mm., n 1.5552.

More conveniently the hydroxymethylene compound may be isolated withbenzene instead of ether. In that case the formic acid is removed whendistilling off the benzene, and the crude undistilled hydroxymethyleneketone may be used for the next stage.

Ethyl vinyl ketone adduct (VII ).-A solution of fresh- 1y distilledethyl vinyl ketone (15.0 g.) and distilled hydroxy-methylene ketone(V11) (29.0 g.) are dissolved in dry redistilled tert-butanol (120 cc.).The solution is cooled in ice, the air is displaced with nitrogen, and asolution of potassium tert-butoxide, prepared by dissolving potassium(600 mg.) in dry tert-butanol (22.5 cc.), is added. The solution iscooled until the butanol just starts to crystallize. The air is againdisplaced with nitrogen, and the solution is left at room temperaturefor hours. On scratching a heavy precipitate separates; the mixture isice-cooled, the adduct is filtered and washed with cold butanol. Onbeing dried, the white sparkling plates melt at 98 C.

T ricyclic ketone (VIII) .-The crystalline ethyl vinyl ketone adduct(VII) (18.9 g.) is dissolved in redistilled dioxan (760 cc.) and thesolution is cooled in ice. A cooled solution of potassium hydroxide (19g.) in water (760 cc.) is added, and the solution is allowed to stand atroom temperature (ca. 30) for 3 hours with occasional shaking. Thinitially clear solution becomes turbid after a few minutes and a smallupper layer separates. ther and water are added, the aqueous layer iswashed twice with ether, the combined organic extracts are washed withwater until neutral, and are then dried and evaporated. The dioxan isfinally removed at the water pump, when the residue on being cooledcompletely solidifies. Cry-stalliz-ation from methanol yields thetricyclic ketone (VI-Ill) as prisms, -M. P. 70.572.5 C.

Tricyclic ketone glycol (IX ).Osmium tetoxide (32.394 g.) is dissolvedin Na-dried ether (350 cc.) or in benzene and ether. cc.- benzene, tomake a'27% solution, plus 250 cc. ether) and cooled. The 0504 solutionis added to a cooled ether solution (730 cc.) of tricyclic ketone(Vii-II) (29.791 g.; 20 mg. in excess'of calculated amount) withswirling. The solution is set aside at room temperature in a dark placefor 5 to 8 days. The ether solution is decanted through a filter, andthe complex is dissolved in methylene dichloride (500 cc.) and shakenmechanically with a solution of mannitol (167 g.) and potassiumhydroxide (47.5 g.) in water (1250 cc.) for 1 hour or until themethylene chloride layer is very pale yellow. The methylene chloridelayer is separated; the aqueous layer is saturated with sodium chlorideand extracted four times with chloroform. The combined CI-I2C12CHC13extracts are washed twice with saturated sodium chloride solution, driedwith anhydrous Na2SO4, and concentrated on the steam bath and in vacuo.The residual gum is triturated with benzene cc.). After cooling somewhatthe white solids are filtered off. They melt at -150" C., and give thedesired glycol (IX), M. P. 152156 C., after one recrystallization fromCHcla-benzene.

Tricyclic isopropylidine ketone (X ).-The tricyclic ketone glycol (IX)(20 g.) is placed in a strong 2-liter Pyrex bottle with anhydrous CuSO4(100 g.) and dry acetone (2000 cc.). The bottle is stoppered securelyand shaken mechanically for 36 hours. The CuSO4 is removed by filtrationthrough sintered glass, and the acetone solution is shaken with a smallamount of anhydrous KzCOs, filtered, and evaporated to dryness using aWater aspirator. The residue, on crystallization from benzene-petroleumether, gives the isopropylidene compound (X), M. P. 95- 98 C.

Mono-unsaturated tricyclic isopropylidene ketone (XI).-The tricyclicisopropylidene ketone (X) (14.727 g.) is stirred in an atmosphere ofhydrogen in the presence of prereduced 2% palladium on strontiumcarbonate catalyst (7.3 g.) in 100 cc. Na-dried benzene. In 3 hours 25minutes, 1224 cc. hydrogen has been absorbed by which time theabsorption of hydrogen has become drastically slower and the reductionis stopped. The catalyst is filtered off through a sintered glassfunnel, and Washed with reagent grade benzene, and most of the benzeneis removed in vacuo. The residual solution is diluted with petroleumether and the mono-unsaturated tricyclic ism propylidene ketone (XI)separates as a fine white powder, M. P. 153156 C.

Hydroxymethylene mono-unsaturated tricyclic isopropylidene ketone(XII).In an atmosphere of nitrogen, freshly prepared sodium methoxide(13.1 g.) is covered with dry benzene (175 cc.) and K2CO3 dried anddistilled ethyl formate (33 cc.) is added to the stirred mixture in athin stream. The mixture is stirred at room tempertaure for 30 minutes,and a solution of the monounsaturated tn'cyclic isopropylidene ketone(24 g.) in dry benzene cc.) is added. Stirring at room temperature iscontinued for about 1 hour or until the mixture has solidified to agelatinous mass. After standing under nitrogen overnight, phosphatebuffer solution (1406 cc.;-156 cc. 0.7 M KH2PO4 plus 1250 cc. 0.7 MNazHPOi) is added with stirring, and the layers are separated, The pH ofthe aqueous layer is adjusted to pH 8 by adding a few cc. of the KHzPOisolution, if necessary. The solution is extracted with ether 4 times,the combined organic layers are dried with N32S04 and concentrated todryness on the steam bath and in vacuo. The crude hydroxymethylenecompound (XII) solidifies when all the solvent is removed.

Methylanilino derivative (XIlI).--The crude hydroxymethylene compound(XII) (29 g.) is dissolved in methanol (275 cc.) and methylaniline (57cc.). After standing overnight the-yellow crystalline methylanilinocompound (XIII) is filtered oil and washed with petro- 9 leum etheruntil the odor of methyl aniline can not be detected. It melts at2l8-222.5 C.

Cyanoethyl derivatives (XI Va and XIb).The methylanilino derivative(XIII) is reacted with acrylonitrile in tertiary butanol solution in thepresence of Triton B and a small amount of water. The acrylonitrilecondenses at position 1 of the methylanilino compound with shift of thedouble bond to give the stereoisomeric cyanoethyl derivatives (XIVa andXIVb). V

carboxyethyl derivatives (X Va and X Vb) .The cyanoethyl derivatives(XIVa and XIVb) are preferably not separated but are converted to thecorresponding carboxyethyl derivatives by vigorous basic hydrolysis. Thecyanomethyl compounds are subjected to boiling aqueous sodium hydroxidefor about 6 hours. The isomeric carboxyethyl compounds are isolated byacidification and filtration, and after drying are taken up in ether.isomer XVa separates from the ether as crystals which may appear in alabile form melting at 150 C. or a stable form melting at 170 C. IsomerXVb is obtained as an oil by evaporation of the ether.

Enol lactone (XVI).The oily carboxyethyl isomer (XVb) is added to aceticanhydride, boiled for several hours, a small amount of sodium acetate isadded and the mixture is boiled for another hour, forming the enollactone (XVI). The highest melting point of this compound has been 240but material melting above 195 C. is satisfactory for further reaction.

D-homosteroid (XVII).The enol lactone (XVI) is dissolved in ether or amixture of ether and benzene and one mole of methyl Grignard reagent isadded. The condensation product is decomposed with acid and treated withdilute alkali in aqueous methanol or dioxane giving the D-homosteroid(XVII), melting point, 205 C.

Dialdehyde (XVI1I).-Compound (XVII) is dissolved in aqueous dioxane,periodic acid is added and the mixture is allowed to stand at roomtemperature overnight. This treatment hydrolyzes the acetonyl glycol tothe free 10 glycol and oxidizes the latter to the dialdehyde XVIII,melting point C.

Steroid (XIXa).--The dialdehyde (XVII) is heated in aqueous dioxane atC. for 6 hours. This treatment recloses ring D to give the 17-aldehydesteroid (XIXa), melting point 173 C. Some of the isomeric 15-aldehyde(XIXb), melting point 150 C., is also produced. Comparison ofderivatives of the 17-aldehyde with similar derivatives of the naturallyoccuring steroid hormones of the adrenal cortex, such as Kendallscompound E, shows that the 17-aldehyde is identical in stericconfiguration with the natural steroid hormones.

Subject matter disclosed in this application is claimed in myapplications Serial Nos. 269,328, now Patent No. 2,681,366; 269,329, nowPatent No. 2,672,482, and 269,- 330, now Patent No. 2,701,807, filedJanuary 31, 1952.

I claim:

The method of converting the cis-adduct of 1,3-butadiene andZ-methyl-S-methoXybenzoquinone into the trans-adduct which comprisesdissolving the cis-adduct in an alkaline aqueous organic solvent andacidifying the solution in the presence of solid crystals of thetransadduct whereby the trans-adduct crystallizes out of the solution.

References Cited in the file of this patent UNITED STATES PATENTS2,379,494 Orchin et a1. July 3, 1945 2,406,652 Ballard 'Aug. 27, 19462,500,385 Schmerling Mar. 14, 1950 2,533,124 Levin Dec. 5, 19502,542,223 Wendler Feb. 20, 1951 OTHER REFERENCES Gilman: OrganizedChemistry, vol. 1, pp. 375-379, (1938), John Wiley & Sons, Inc. NewYork.

Orchin et al.: Jour. of Organic Chemistry, vol. 8, pp. 509-14, (1943).

